How to Identify Canker Sores and their Stages.
Canker sore (aphthous ulcer) identification.
Dentists distinguish canker sores (specifically, “recurrent minor aphthous ulcers,” the common type of canker ulceration that affects 80% of sufferers) from other types of mouth sores based on these three points.
The three pillars of canker sore identification –
- Their appearance (which changes during their successive stages of formation and then healing).
- Their location and the type of oral tissue on which they’ve formed.
- The fact that they are recurrent (meaning the person has experienced them before).
Additionally, the person’s Patient History (in terms of what they specifically did or did not experience with their sores) can also play a valuable role in identification and helps to differentiate this type of lesion from other kinds of mouth sores. For example: Canker sores vs. Oral herpes. - Telling the two apart.
Methods that aren’t routinely used for aphthous ulcer identification.
As a side note, we’ll point out that the factors mentioned above, collectively, are usually all that’s needed to make an accurate diagnosis for canker sores.
- No medical testing (e.g. biopsy, culturing) is typically involved in making a diagnosis.
- We’ll also mention that when viewed microscopically, the histologic characteristics of canker sores are non-specific and therefore this method of examination isn’t especially useful in identification.
(Visit this page if you’d like information about The biology of canker sore formation. )
What do canker sores look like?
The appearance of a canker sore will change as it advances through its successive stages of formation and then healing.
The stages –
As additional help in understanding this topic, we also have Q & A sections that answer questions people frequently have about canker sore identification and their stages.
(Note: The time frames we’ve assigned to each of the stages below overlap because what any one person experiences varies.)
#1 – The Prodromal Stage.
(Also referred to as the Premonitory Stage.)
Time frame: 2 to 48 hours duration.
This stage is the earliest indication of pending canker sore formation but it doesn’t involve any visible signs. Instead, what’s noticed is a tingling, itching, burning, or numb sensation in the area where the lesion will ultimately form.
These kinds of signs are referred to as “prodromal” symptoms, meaning that they hint that something is brewing but the signs themselves are not specific just for canker sores.
# 2 – The Macule Stage.
(Also referred to as the Preulcerative Stage.)
Time frame: 18 to 72 hours duration.
During this time frame, the first visible signs of the developing lesion will have started to show.
- The area where the sore will ultimately form begins to transform into a reddened circular area on the skin. (Formally referred to as an “erythematous macule.”)
- As the lesion’s development progresses, it’s possible that the macule may transform into a small, possibly whitish, papule (solid, slightly raised area).
- Toward the end of the macule stage, the tissue of the affected area will begin to ulcerate.
(This process of ulceration begins in the skin’s basal (lowest) layer and then becomes more apparent as it advances up into the more superficial layers above.)
Slideshow – Canker sore pictures.
Pictures of fully formed aphthous ulcers.
#3 – The Ulcer Stage.
By this stage in its development, the lesion has transformed into a fully-formed ulceration. It may continue to grow in size for 4 to 6 days.
What does a canker sore ulceration look like?
- In basic form, the lesion is a single shallow ulcer having a symmetrical round or oval shape. (Multiple simultaneous lesions are possible.)
- Canker sores are typically no more than 1/4 inch in diameter (3 to 5 mm).
Diagram: The physical characteristics of a canker sore.
Sores have a grayish membrane-coated central ulceration with a surrounding red border. The skin around the lesion looks normal.
- The lesion’s center (the ulceration) develops a loosely attached membrane-like covering (a pseudomembrane) that can be easily dislodged.
(The membrane is pyogenic in nature, meaning it’s composed of cells, compounds, and debris originating from the inflammatory process that has caused the ulceration.)
- Initially, the membrane has a primarily yellow-white coloration. As healing ultimately progresses, it will tend to take on more of a grey-white tint.
- A border comprising a band of erythematous (reddish) tissue will surround the ulceration.
The outline of this red halo is characteristically circumscribed (well defined) and regular (not jagged).
- The skin that lies outside the lesion’s reddened border will appear normal and healthy.
Other characteristic signs and symptoms.
- Canker sores usually are painful. The level of discomfort that’s experienced may seem out of proportion with the lesion’s size.
Sufferers will frequently limit their oral movements, the types of foods they eat, and favor the sore’s surface as not to trigger pain.
- There are no distinguishing systemic features associated with minor aphthous ulcers, such as the person having malaise (generally feeling poorly) or fever.
Can a person have more than one lesion at a time?
Yes, outbreaks of multiple, simultaneous canker sores may occur.
- Usually, the maximum number of sores that will form at one time will be six or fewer.
- If multiple canker sores do develop, they’re more likely to be distributed as opposed to being clustered together.
- In the case where two sores do form adjacent to each other, they may combine into a single larger and irregularly shaped ulcer (as opposed to the classic round or oval shape).
▲ Section references – Neville
Are they contagious?
- No, canker sores are neither contagious nor infectious.
For more details, see this page Why canker sores are not contagious.
Where do canker sores form?
They characteristically only form on the “loose” (movable) tissues of the mouth, meaning those areas where the skin is not tightly bound to the bone underneath. These locations generally involve the “nonkeratinized” (softer, less tough) tissues of the mouth.
Location, location, location.
An important aspect of canker sore identification is based on the fact that they characteristically only form in certain parts of the mouth. These locations are, listed here in order of locations/tissues most affected:
Diagram: Locations where canker sores usually form.
Canker ulcerations characteristically form on the “loose” tissues of the mouth.
- The inside surface of the lips and cheeks.
- The underside (ventral surface) of the tongue.
- The mucobuccal fold (the deep trough where the skin of the jawbones and lips/cheeks meet).
- The floor of the mouth.
- The soft palate.
- The tonsillar areas.
(Listed in order of locations/tissues most affected.)
Less common locations.
While rare, it is possible for canker sores to form on keratinized tissues. This includes the top (dorsal) surface of the tongue, the gum tissue that surrounds a person’s teeth, hard palate, or even the border of the lips (vermilion border).
▲ Section references – Neville, Dunlap
Additional Q & A about the formation stages.
Beyond the questions we’ve addressed above, here are some additional ones that people often have.
Can you pop a canker sore?
No, aphthous ulcers form from a macule (reddened area of skin), not a blister. There is never any blister to pop.
Why are canker sores so painful?
These lesions are ulcerations. The protective layer of skin that originally covered over the area of the sore has fully deteriorated thus leaving the inner layer of tissue and the nerve endings it contains exposed.
FYI: Some treatments for canker sores work by forming a protective film over the ulceration.
Do canker sores get bigger before they go away?
With “recurrent minor aphthous ulcers” (the most common type of canker ulceration), once a lesion has fully formed (usually by day 4 to 6), it’s not expected to grow in size. However, during formation, it is possible for two directly adjacent lesions to coalesce into one larger one.
Is it normal for canker sores to be yellow?
Yes. Especially during the early stages of ulcer formation, a yellow membrane can usually be seen covering its surface. Later on, this yellow coloration will typically transform to a grey-white tint.
#4 – Canker sore healing stages.
Time frame: 4 to 14 days duration.
The Healing stage time frame.
Canker sores (specifically, recurrent minor aphthous ulcers) characteristically heal within just a few to several days. This characteristic can be used to help confirm the kind of lesion a person has.
How long should it take for a canker sore to heal?
- A sore will usually heal within 4 to 14 days, although some can heal in as little as 3 to 5.
- The pain associated with a lesion will usually begin to subside around day 3 or 4.
- In most cases, the process is uneventful and results in no residual scarring.
When should I be concerned about a canker sore?
Any ulcer that has not healed within a 2-week time frame should be evaluated by a dentist. This is for two reasons.
- One is for proper lesion differentiation. (Is the lesion really a canker sore?)
- The other is because there is another larger, more problematic form of aphthous ulcer that characteristically does have an extended healing time frame and its needed management is different than with routine canker sores.
Canker sore appearance during its healing stages.
- The process of new skin growth (epithelialization) will start off at the edges of the ulcerated area and then, as days pass, advance from all directions until finally the wound’s entire surface has been covered.
- As this epithelialization process takes place, the original yellow-white color of the sore will take on a grey-white appearance.
- As the newly formed tissues mature (the surrounding edges of the wound will be at a more advanced state than its center), the skin will begin to take on a more normal pink coloration and the size of the lesion will continually shrink down.
- The reddened border of the original wound will remain obvious during the early stages of the healing process. Then, as the new skin tissue matures, the border’s redness will fade until finally complete healing has occurred and the skin’s normal appearance returns.
How can you tell that your canker sore is healing properly?
As long as the changes you notice with your lesion’s healing progress stay within the time frame and appearance parameters just discussed, you can assume that all is going well.
Reasons for concern.
Any events that vary from what’s described above should trigger some concern and is a reason to consult with your dentist.
- Top on the list of issues that should be investigated is if the lesion is indeed a canker sore (“recurrent minor aphthous ulcer”), as opposed to a lesion of a different cause.
- If the lesion is determined to be an aphthous one, your dentist should then determine if instead of a “minor” lesion it is a “major” one. And therefore a type of sore that needs an extended time frame and possibly more aggressive management to resolve.
Additional Q & A about the healing stages.
Beyond the questions we’ve addressed above, here are some additional ones that people often have.
Do canker sores hurt more when healing?
No, once the full extent of the ulceration has formed, your sore’s healing will begin and the level of pain associated with it should start to improve.
The new reparative tissues will first start to form around the edges of the lesion and then continue to close in over its entire surface as days pass. As the size of the raw, uncovered portion of the ulceration continues to diminish, the level of pain associated with the lesion should diminish.
How long does the pain of a canker sore last?
Hopefully, the level of discomfort you notice will start to subside by days 3 to 4. Although, complete resolution of pain won’t occur until that point when the healing process has advanced enough that the exposed tissues of the lesion are finally covered over and protected.
What color do canker sores turn when healing?
It’s normal for the original yellow-white color of the ulceration to transform to a grey-white tint. This is a sign of primordial skin tissue formation.
How do you know when a canker sore is healing?
As the process of forming new skin over the lesion progresses (epithelialization), its surface will start to take on a grey-white tint.
Since the edges of the ulceration will mature sooner than its center, this area will be the first to return to a more normal pink coloration. As new skin forms over more and more of the sore’s surface, the amount of pain the lesion causes will diminish.
How many days does it take for a canker sore to go away?
This will depend on the initial size of the ulceration and ultimately how involved its healing process will be.
With small sores, it’s possible that resolution may occur as quickly as just several days (3 to 5). But with relatively larger lesions, expect that it may take as long as two weeks.
What happens if a canker sore goes untreated?
In the vast majority of cases, no treatment is required for a canker sore and its healing will occur uneventfully and without scarring.
FYI: Most over-the-counter treatments for aphthous ulcers are only palliative in nature. (Only aimed at reducing pain levels and maintaining a healthy wound as opposed to speeding up healing.)
How often do canker sores form?
- Once a person has experienced an initial outbreak, the probability of recurrence is high, although the frequency with which this takes place can be quite variable.
- A rate of one outbreak every 1 to 3 months might be considered typical (encompassing about 50% of people who get them). 30% of sufferers deal with their presence on a monthly basis.
That means many people will only be plagued by a few episodes a year, while others will experience nearly continuous outbreaks and therefore will never be completely free of ulcers for any extended period of time.
Incidence rates / Prevalence.
- Most sources tend to suggest that around 20% of the general population experiences canker sores, although actual reports from studies have ranged from 5% to 66%.
- A person’s first outbreak will typically take place between the ages of 10 and 20 (teen years through young adult), and then decrease in frequency and severity with age.
Lesions are most prevalent in people ages 10 to 40. 80% of those affected will experience their first lesion prior to the age of 30.
- It’s been suggested that women are more likely to experience sores than men but not all studies confirm this fact.
- A family (genetic Details) predisposition seems to exist. Children with parents who get canker sores have a 90% chance of getting them too, as compared to a 20% chance for those whose parents don’t.
- A person’s risk seems to be unrelated to race. But people who live in North America are more likely to suffer from them, as opposed to people who live in other worldwide geographic areas.
- Non-smokers and people in upper socioeconomic groups are more likely to experience outbreaks.
What are “major aphthous ulcers”?
Canker sores like we have described above are formally termed “recurrent minor aphthous ulcers.” They are the type of canker lesion experienced by 80% of sufferers.
Beyond these “minor” lesions, there’s another type of aphthous ulcer referred to as “major aphthae” or Sutton’s ulcers. And in comparison to the minor variety, these “major” canker sores are large, deep ulcerations whose healing is characteristically slower and more painful.
- Unlike minor aphthae, the major kind forms on all types of oral tissues (both keratinized and nonkeratinized tissues). They frequently form on the lips, soft palate, or fauces of the throat.
- They can approach 1/2 inch (or more) in diameter and may cause regional or even facial swelling.
- Their healing usually takes between 10 and 40 days. However, it may take some months (even as new ulcers are forming).
- Residual scarring is common.
▲ Section references – Chavan, Neville
Page references sources:
Akintoye SO, et al. Recurrent aphthous stomatitis.
Casiglia J. Recurrent aphthous stomatitis: Etiology, diagnosis, and treatment.
Chavan M, et al. Recurrent aphthous stomatitis: a review.
Dunlap CL, et al. A guide to common oral lesions.
Neville BW, et al. Oral and Maxillofacial Pathology. Chapter: Allergies and Immunologic Diseases.
Scully C, et al. Oral medicine — Update for the dental practitioner Aphthous and other common ulcers.
Ship J, et al. Recurrent Aphthous Stomatitis.
Ship II. Epidemiologic aspects of recurrent aphthous ulcerations.
Woo S, et al. Recurrent Aphthous Ulcers: A Review of Diagnosis and Treatment.
All reference sources for topic Canker Sores.